1. Field of the Invention
The present invention relates to a wiper device which wipes a glass surface such as a windshield glass of a vehicle.
2. Description of the Related Art
A wiper device for wiping a windshield glass or the like of a vehicle comprises a wiper arm and a wiper blade held by a wiper arm.
In the wiper arm, an end portion of an arm head is fixed to a pivot shaft and a retainer is connected to the other end portion of the arm head so as to be pivotable with respect to a predetermined angle. A spring is provided between the arm head and retainer so as to constantly urge the retainer toward a wiping object surface such as a windshield glass. An arm piece is fixed to a front end portion of the retainer. A front end portion of the arm piece is bent in the form of a substantially U shape and holds the wiper blade. On the other hand, the wiper blade comprises a blade rubber which is in contact with the wiping object surface for wiping it and a plurality of holding levers for holding this blade rubber.
When the wiper device is actuated, the wiper arm and wiper blade rotate by reciprocation, so that the blade rubber moves on the windshield glass while closely contacting the glass, so as to wipe off rain drops.
As the wiper device of a vehicle, currently a wide range wiping type having an expandable wiper arm has been proposed to eliminate as far as possible regions left unwiped in the entire range of the windshield glass (enlarge the wiping range). Further, as one example of this wide range wiping type, a wiper device provided with a wiper arm called a four-articulation link system has been particularly well known (as an example, EP0182123).
This wiper device of the vehicle having a wiper arm called the four-articulation link system includes a main lever (first lever) and a sub lever (second lever) acting as a pair. The main lever is connected to and fixed to a pivot shaft and the sub lever is supported, such that rotation is possible, by a supporting shaft provided at a position set a predetermined distance apart from the pivot shaft. Further, the main lever and the sub lever are disposed in parallel and an arm head (third lever) is rotatably connected to a front end of each.
If the main lever rotates with the pivot shaft, the arm head linked with the sub lever rotates such that it approaches or leaves with respect to the pivot shaft and as a result, the entire length of the wiper arm expands or contracts. As a result, the entire length of the wiper arm apparently expands at a predetermined wiping position so as to expand the wiping range. Therefore, in a case wherein a windshield glass the longitudinal dimension of which is set relatively long is wiped, as compared to a wiper device (wiper device in which the arm head is directly fixed to the pivot shaft and the wiper arm and wiper blade simply rotate by reciprocation around the pivot shaft) provided with an ordinary wiper arm, it is difficult for unwiped regions to remain in the entire range of the windshield glass.
In the wiper device of the vehicle having a wiper arm of this kind of the four-articulation link system, the main lever and sub lever disposed in parallel and rotating as described above, and the arm head to which they are attached, together form a link mechanism. If snow or the like adheres to or remains at a traveling range of this link mechanism, it becomes a cause for obstructing a smooth operation of the wiper device. Thus, it is necessary to take measures to prevent snow from remaining and prevent the amount of snow that has entered from increasing. Particularly, it is necessary to take measures to prevent foreign matter such as a bough from entering the link mechanism without being prepared for it.
Covering all of the aforementioned levers with an engine hood of a vehicle so that they are not exposed to the outside can be considered, but because the main lever and the sub lever and further the arm head linked therewith move over a relatively wide range, it is difficult to secure such a traveling space within the engine hood and to cover the entire range completely.